TROP-2 is a cell surface glycoprotein expressed on most carcinomas, as well as some normal human tissues. It was initially defined as a molecule recognized by two murine monoclonal antibodies raised to a human choriocarcinoma cell line BeWo that recognized an antigen on human trophoblast cells (Faulk 1978). The same molecule was independently discovered by other investigators which led to multiple names describing the same antigen. Hence, TROP-2 was also referred to as GA733-1 and epithelial glycoprotein-1 (EGP-1) (Basu 1995, Fomaro 1995).
The TROP-2 gene is an intronless gene that was thought to have been formed through the retroposition of a homologous gene GA 733-2 (also known as epithelial glycoprotein-2, EpCAM and Trop-1) via an RNA intermediate. The TROP-2 gene has been mapped to chromosome 1p32 (Calabrese 2001). The protein component of TROP-2 has a molecular mass of approximately 35 kilodaltons. Its mass may be increased by 11-13 kilodaltons with heterogeneous N-linked glycosylation of its extracellular domain. There are many cysteine residues in the extracellular domain which could form disulfide bridge sites. TROP-2 is a substrate for protein kinase C, a Ca2+ dependent protein kinase and the intracellular serine 303 residue has been shown to be phosphorylated (Basu 1995). It has also been shown that crossing-linking of TROP-2 with anti-TROP-2 antibodies transduced a calcium signal as shown by a rise in cytoplasmic Ca2+ (Ripani 1998). These data support signal transduction as a physiological function of TROP-2, although to date no physiological ligand has been identified. Recently an association between TROP-2 expression and cancer has been shown as TROP-2 was identified as a member of a group of genes reported to be the most highly overexpressed in ovarian serous papillary carcinoma compared to normal ovarian epithelium in a large-scale gene expression analysis using cDNA microarray technology (Santin 2004).
The expression profile of TROP-2 has been elucidated through immunohistochemistry (IHC) and flow cytometery studies using many different TROP-2 antibodies. Anti-TROP-2 antibodies 162-25.3 and 162-46.2 were produced through immunization of mice with the human choriocarcinoma cell line BeWo, and were investigated for their reactivity to a series of tumor and lymphoid cell lines and peripheral blood mononuclear cells. In this study both antibodies appeared to be trophoblast specific, staining 3 of the 4 choriocarcinoma cell lines tested, while none of the other lymphoid or tumor cell lines (representing fibrosarcoma, cervical sarcoma, colon carcinoma, melanoma, neuroblastoma, erythroleukemia) were stained in an indirect immunofluorescence FACS assay. In addition, none of the normal peripheral blood cells were stained. The antibodies were tested for staining of formalin-fixed paraffin-embedded placenta tissue sections and frozen normal sections of liver, kidney, spleen, thymus and lymph node tissues. The placenta tissue sections were stained with both antibodies, while there was no staining of the other normal tissues (Lipinski 1981). These two antibodies have strictly been reported for use in in vitro diagnostic studies.
Anti-TROP-2 antibody MOv16 was generated through the immunization of mice with a crude membrane preparation of poorly differentiated ovarian carcinoma OvCa4343/83. MOv16 was tested for reactivity to a series of frozen tissue sections of benign and malignant ovarian tumors. MOv16 reacted with 31 of 54 malignant ovarian tumors and 2 of 16 benign ovarian tumors. Of the 5 mucinous ovarian tumors that were tested, MOv16 was completely unreactive. MOv16 was also tested for reactivity to frozen sections of non-ovarian malignant tumors where it was found to bind 117 of 189 breast carcinoma sections and 12 of 18 lung carcinoma sections. MOv16 was completely unreactive on 16 non-epithelial tumors that were tested (including liposarcomas, chondrosarcomas, endotheliomas, histiocytomas and dysgerminomas). When tested on frozen normal tissue sections, MOv-16 was reactive with breast, pancreas, kidney and prostate sections. MOv16 reactivity was reported to be negative on lung, spleen, skin, ovary, thyroid, parotid gland, stomach, larynx, uterus and colon sections, though the number of tissue sections that were used was not reported. The authors noted that frozen tissue sections were used because MOv16 was unreactive to paraffin embedded tissues (Miotti 1987). This antibody has also only been reported for use in in vitro diagnositic studies.
Anti-TROP-2 antibody Rs7-3G11 (RS7) was generated through the immunization of mice with a crude membrane preparation derived from a surgically removed human primary squamous cell carcinoma of the lung. IHC was used to examine the staining of RS7 on frozen sections of human tumor and normal tissues. RS7 bound to 33 of the 40 sections representing tumors of the breast, colon, kidney, lung, prostate and squamous cell cancer. Of the normal tissues RS7 bound to 16 of 20 sections of breast, colon, kidney, liver, lung and prostate tissues while none of the five sections of spleen tissue were stained. In this study the authors noted that it appeared that antigen density in tumors was higher than in normal epithelial tissues (Stein 1990).
Additional studies of the tissue specificity of RS7 were carried out on both tumor and normal tissues. RS7 was tested on a panel of frozen tumor sections and bound to 65 of the 77 sections representing tumors of the lung, stomach, kidney, bladder, colon, breast; ovary, uterus and prostate. There was no binding to the 5 lymphomas tested. RS7 was tested on a panel of 85 frozen human normal tissue sections composed of a total of 24 tissue types. 39 sections of 13 normal tissues (lung, bronchus, trachea, esophagus, colon, liver, pancreas, kidney, bladder, skin, thyroid, breast and prostate) were stained by RS7. The authors of this study noted that in the tissues in which positive staining was observed, the reactivity was generally restricted to epithelial cells, primarily in ducts or glands. It was also noted that this study was limited to frozen sections since it was observed that RS7 was not reactive on formalin-fixed paraffin-embedded sections (Stein 1993).
Polyclonal anti-TROP-2 antibodies were prepared by immunizing mice with a synthetic peptide corresponding to amino acid positions between 169 and 182 of the cytoplasmic domain of human TROP-2. The polyclonal antibodies were tested on a tissue array slide that contained formalin-fixed human esophageal hyperplasia and carcinoma tissues. Ten of the 55 carcinoma specimens displayed heavy staining with the polyclonal antibodies, while the mild hyperplasia tissue stained very weakly, indicating expression levels may be related to malignant transformation (Nakashima 2004).
Overall, IHC reactivity patterns obtained with different anti-TROP-2 antibodies were consistent. Expression in cancer was seen primarily in carcinomas, and most carcinomas were reactive. In normal tissues, expression appeared to be limited to cells of epithelial origin, and there was some evidence that staining of carcinomas was stronger than staining of corresponding normal epithelial tissues.
In addition to being used in IHC studies, antibody RS7 was tested in in vivo models with initial experiments consisting of tumor targeting studies in nude mouse xenograft models. Radiolabeled RS7 injected i.v. was shown to accumulate specifically in the tumor of mice bearing either Calu-3 (lung adenocarcinoma) or GW-39 (colon carcinoma) tumors (Stein 1990). Further studies were done to investigate the biodistribution of radiolabeled RS7 in a xenograft system and to study the therapeutic potential of RS7 as an immunoconjugate. In this study the therapeutic efficacy of 131I-labeled RS7 F(ab′)2 was investigated in nude mice bearing Calu-3 human lung adenocarcinoma xenografts. Three weeks following inoculation of the mice with Calu-3 cells, when the tumors had reached a size of approximately 0.3-0.9 grams, groups of 6-7 mice were treated with a single dose i.v. of either 1.0 mCi 131I-RS7-F(ab′)2 or 1.5 mCi 131I-RS7-F(ab′)2 and compared to a similar group of untreated control mice. The single dose of 1.0 mCi 131I-RS7-F(ab′)2 resulted in tumor growth suppression for approximately 5 weeks, while the single dose of 1.5 mCi 131I-RS7-F(ab′)2 resulted in tumor regression, and the mean tumor size did not exceed the pre-therapy size until the eighth week after radioantibody injection. Mice receiving the 1.5 mCi 131I-RS7-F(ab′)2 dose experienced a mean body weight loss of 18.7 percent, indicating there was toxicity associated with the treatment. In this study, effects of treatment with naked RS7 or the F(ab′)2 fragment of RS7 were not tested (Stein 1994a). Another study was done to test the efficacy of 131I-RS7 in a MDA-MB-468 breast cancer xenograft model. Groups of ten mice bearing MDA-MB-468 tumors of approximately 0.1 cm3 were treated with a single dose i.v. of either 250 microcuries 131I-RS7 or 250 microcuries 131I-Ag8 (an isotype matched control antibody). Groups of six mice were treated with a single dose i.v. of 30 micrograms of either unlabeled RS7 or Ag8. Complete regression of the tumors (except for one animal that had a transient reappearance of tumor) was seen in the animals treated with 131I-RS7, which lasted for the duration of the 11 week observation period. Tumor regression was also seen in 131I-Ag8 treated mice, though was only observed between 2 weeks and 5 weeks with tumors either persisting or continuing to grow for the remainder of the study. Tumor growth of mice that received unlabeled RS7 or Ag8 was not inhibited and there did not appear to be any differences in the mean tumor volume of RS7 treated mice compared to the Ag8 treated mice. Two additional groups of 10 mice bearing larger MDA-MB-468 tumors of approximately 0.2-0.3 cm3 were treated with a slightly higher single dose of either 275 microcuries 131I-Rs7 or 275 microcuries 131Ag8 and compared to a similar group of untreated mice. Tumor volume was measured weekly for 15 weeks. Although in this case there was a significant difference in tumor growth between the 131I-RS7 treated mice compared to the untreated mice, there was no significant difference in the tumor growth of the 131I-RS7 compared to the 131I-Ag8 treated mice, indicating a portion of the efficacy may have been due to non-specific effects of the radiation. Unlabeled antibodies were not tested in mice containing 0.2-0.3 cm3 tumors (Shih 1995).
There have been numerous additional studies examining the efficacy of RS7 as an immunoconjugate with an attempt to select the optimal radiolabel for radioimmunotherapy (Stein 2001a, Stein 2001b, Stein 2003). A humanized version of RS7 has also been generated, however it has only been tested in preclinical xenograft models as a radioconjugate (Govindan 2004). These studies show similar positive effects as the previously described studies with RS7, however in one study, even when radiolabeled RS7 was delivered at a previously determined maximum tolerable dose, toxicity occurred leading to death in some mice (Stein 2001a). Although effective treatment of xenograft tumors in mice was achieved with radiolabeled RS7 in these studies, naked RS7 was not evaluated.
Immunizing mice with neuramindase pre-treated H3922 human breast carcinoma cells produced the anti-TROP-2 monoclonal antibody BR110 (as disclosed in U.S. Pat. No. 5,850,854, refer to Prior Patents section). By immunohistology, using human frozen tissue specimens, BR110 was shown to react with a wide range of human carcinoma specimens including those of the lung, colon, breast, ovarian, kidney, esophagus, pancreas, skin, lung and tonsil. No human normal tissue sections were tested. In vitro studies demonstrated that BR110 had no ADCC or CDC activity on the human carcinoma cell lines H3396 or H3922. In vitro studies analyzing the cytotoxicity of BR110-immunotoxins was performed on the human cancer cell lines H3619, H2987, MCF-7, H3396 and H2981. The EC50 for the cell lines tested was 0.06, 0.001, 0.05, 0.09 and >5 micrograms/mL respectively. No cytotoxicity data was disclosed for the naked BR110 antibody. No in vivo data was disclosed for the naked or immunoconjugated BR110.
A number of additional antibodies have been generated that target TROP-2, such as MR54, MR6 and MR23 which were generated from immunization of mice with the ovarian cancer cell line Colo 316 (Stein 1994b) and antibody T 16 which was generated by immunization of mice with the T24 bladder cancer cell line (Fradet 1984). The use of these antibodies has been limited to biochemical characterization of the TROP-2 antigen and cell line and tissue expression studies. There have been no reports of anti-cancer efficacy of these antibodies, either in vitro or in vivo. RS7 was the only antibody that was tested for therapeutic efficacy in preclinical cancer models, with its use being limited to a carrier of radioisotope. There are no reports of any naked TROP-2 antibodies exhibiting therapeutic efficacy in preclinical cancer models either in vitro or in vivo.
Monoclonal Antibodies as Cancer Therapy: Each individual who presents with cancer is unique and has a cancer that is as different from other cancers as that person's identity. Despite this, current therapy treats all patients with the same type of cancer, at the same stage, in the same way. At least 30 percent of these patients will fail the first line therapy, thus leading to further rounds of treatment and the increased probability of treatment failure, metastases, and ultimately, death. A superior approach to treatment would be the customization of therapy for the particular individual. The only current therapy which lends itself to customization is surgery. Chemotherapy and radiation treatment cannot be tailored to the patient, and surgery by itself, in most cases is inadequate for producing cures.
With the advent of monoclonal antibodies, the possibility of developing methods for customized therapy became more realistic since each antibody can be directed to a single epitope. Furthermore, it is possible to produce a combination of antibodies that are directed to the constellation of epitopes that uniquely define a particular individual's tumor.
Having recognized that a significant difference between cancerous and normal cells is that cancerous cells contain antigens that are specific to transformed cells, the scientific community has long held that monoclonal antibodies can be designed to specifically target transformed cells by binding specifically to these cancer antigens; thus giving rise to the belief that monoclonal antibodies can serve as “Magic Bullets” to eliminate cancer cells. However, it is now widely recognized that no single monoclonal antibody can serve in all instances of cancer, and that monoclonal antibodies can be deployed, as a class, as targeted cancer treatments. Monoclonal antibodies isolated in accordance with the teachings of the instantly disclosed invention have been shown to modify the cancerous disease process in a manner which is beneficial to the patient, for example by reducing the tumor burden, and will variously be referred to herein as cancerous disease modifying antibodies (CDMAB) or “anti-cancer” antibodies.
At the present time, the cancer patient usually has few options of treatment. The regimented approach to cancer therapy has produced improvements in global survival and morbidity rates. However, to the particular individual, these improved statistics do not necessarily correlate with an improvement in their personal situation.
Thus, if a methodology was put forth which enabled the practitioner to treat each tumor independently of other patients in the same cohort, this would permit the unique approach of tailoring therapy to just that one person. Such a course of therapy would, ideally, increase the rate of cures, and produce better outcomes, thereby satisfying a long-felt need.
Historically, the use of polyclonal antibodies has been used with limited success in the treatment of human cancers. Lymphomas and leukemias have been treated with human plasma, but there were few prolonged remission or responses. Furthermore, there was a lack of reproducibility and there was no additional benefit compared to chemotherapy. Solid tumors such as breast cancers, melanomas and renal cell carcinomas have also been treated with human-blood, chimpanzee serum, human plasma and horse serum with correspondingly unpredictable and ineffective results.
There have been many clinical trials of monoclonal antibodies for solid tumors. In the 1980s there were at least four clinical trials for human breast cancer which produced only one responder from at least 47 patients using antibodies against specific antigens or based on tissue selectivity. It was not until 1998 that there was a successful clinical trial using a humanized anti-Her2/neu antibody (Herceptin®) in combination with CISPLATIN. In this trial 37 patients were assessed for responses of which about a quarter had a partial response rate and an additional quarter had minor or stable disease progression. The median time to progression among the responders was 8.4 months with median response duration of 5.3 months.
Herceptin® was approved in 1998 for first line use in combination with Taxol®. Clinical study results showed an increase in the median time to disease progression for those who received antibody therapy plus Taxol® (6.9 months) in comparison to the group that received Taxol® alone (3.0 months). There was also a slight increase in median survival; 22 versus 18 months for the Herceptin® plus Taxol® treatment arm versus the Taxol® treatment alone arm. In addition, there was an increase in the number of both complete (8 versus 2 percent) and partial responders (34 versus 15 percent) in the antibody plus Taxol® combination group in comparison to Taxol® alone. However, treatment with Herceptin® and Taxol® led to a higher incidence of cardiotoxicity in comparison to Taxol® treatment alone (13 versus 1 percent respectively). Also, Herceptin® therapy was only effective for patients who over express (as determined through immunohistochemistry (IHC) analysis) the human epidermal growth factor receptor 2 (Her2/neu), a receptor, which currently has no known function or biologically important ligand; approximately 25 percent of patients who have metastatic breast cancer. Therefore, there is still a large unmet need for patients with breast cancer. Even those who can benefit from Herceptin® treatment would still require chemotherapy and consequently would still have to deal with, at least to some degree, the side effects of this kind of treatment.
The clinical trials investigating colorectal cancer involve antibodies against both glycoprotein and glycolipid targets. Antibodies such as 17-1A, which has some specificity for adenocarcinomas, has undergone Phase 2 clinical trials in over 60 patients with only 1 patient having a partial response. In other trials, use of 17-1A produced only 1 complete response and 2 minor responses among 52 patients in protocols using additional cyclophosphamide. To date, Phase III clinical trials of 17-1A have not demonstrated improved efficacy as adjuvant therapy for stage III colon cancer. The use of a humanized murine monoclonal antibody initially approved for imaging also did not produce tumor regression.
Only recently have there been any positive results from colorectal cancer clinical studies with the use of monoclonal antibodies. In 2004, ERBITUX® was approved for the second line treatment of patients with EGFR-expressing metastatic colorectal cancer who are refractory to irinotecan-based chemotherapy. Results from both a two-arm Phase II clinical study and a single arm study showed that ERBITUX® in combination with irinotecan had a response rate of 23 and 15 percent respectively with a median time to disease progression of 4.1 and 6.5 months respectively. Results from the-same two-arm Phase II clinical study and another single arm study showed that treatment with ERBITUX® alone resulted in an 11 and 9 percent response rate respectively with a median time to disease progression of 1.5 and 4.2 months respectively.
Consequently in both Switzerland and the United States, ERBITUX® treatment in combination with irinotecan, and in the United States, ERBITUX® treatment alone, has been approved as a second line treatment of colon cancer patients who have failed first line irinotecan therapy. Therefore, like Herceptin®, treatment in Switzerland is only approved as a combination of monoclonal antibody and chemotherapy. In addition, treatment in both Switzerland and the US is only approved for patients as a second line therapy. Also, in 2004, AVASTIN® was approved for use in combination with intravenous 5-fluorouracil-based chemotherapy as a first line treatment of metastatic colorectal cancer. Phase III clinical study results demonstrated a prolongation in the median survival of patients treated with AVASTIN® plus 5-fluorouracil compared to patients treated with 5-fluourouracil alone (20 months versus 16 months respectively). However, again like Herceptin® and ERBITUX®, treatment is only approved as a combination of monoclonal antibody and chemotherapy.
There also continues to be poor results for lung, brain, ovarian, pancreatic, prostate, and stomach cancer. The most promising recent results for non-small cell lung cancer came from a Phase II clinical trial where treatment involved a monoclonal antibody (SGN-15; dox-BR96, anti-Sialyl-LeX) conjugated to the cell-killing drug doxorubicin in combination with the chemotherapeutic agent TAXOTERE®. TAXOTERE® is the only FDA approved chemotherapy for the second line treatment of lung cancer. Initial data indicate an improved overall survival compared to TAXOTERE® alone. Out of the 62 patients who were recruited for the study, two-thirds received SGN-15 in combination with TAXOTERE® while the remaining one-third received TAXOTERE® alone. For the patients receiving SGN-15 in combination with TAXOTERE®, median overall survival was 7.3 months in comparison to 5.9 months for patients receiving TAXOTERE® alone. Overall survival at 1 year and 18 months was 29 and 18 percent respectively for patients receiving SNG-15 plus TAXOTERE® compared to 24 and 8 percent respectively for patients receiving TAXOTERE® alone. Further clinical trials are planned.
Preclinically, there has been some limited success in the use of monoclonal antibodies for melanoma. Very few of these antibodies have reached clinical trials and to date none have been approved or demonstrated favorable results in Phase III clinical trials.
The discovery of new drugs to treat disease is hindered by the lack of identification of relevant targets among the products of 30,000 known genes that could contribute to disease pathogenesis. In oncology research, potential drug targets are often selected simply due to the fact that they are over-expressed in tumor cells. Targets thus identified are then screened for interaction with a multitude of compounds. In the case of potential antibody therapies, these candidate compounds are usually derived from traditional methods of monoclonal antibody generation according to the fundamental principles laid down by Kohler and Milstein (1975, Nature, 256, 495-497, Kohler and Milstein). Spleen cells are collected from mice immunized with antigen (e.g. whole cells, cell fractions, purified antigen) and fused with immortalized hybridoma partners. The resulting hybridomas are screened and selected for secretion of antibodies which bind most avidly to the target. Many therapeutic and diagnostic antibodies directed against cancer cells, including Herceptin® and RITUXIMAB, have been produced using these methods and selected on the basis of their affinity. The flaws in this strategy are two-fold. Firstly, the choice of appropriate targets for therapeutic or diagnostic antibody binding is limited by the paucity of knowledge surrounding tissue specific carcinogenic processes and the resulting simplistic methods, such as selection by overexpression, by which these targets are identified. Secondly, the assumption that the drug molecule that binds to the receptor with the greatest affinity usually has the highest probability for initiating or inhibiting a signal may not always be the case.
Despite some progress with the treatment of breast and colon cancer, the identification and development of efficacious antibody therapies, either as single agents or co-treatments, have been inadequate for all types of cancer.
Prior Patents:
U.S. Pat. No. 5,750,102 discloses a process wherein-cells from a patient's tumor are transfected with MHC genes which may be cloned from cells or tissue from the patient. These transfected cells are then used to vaccinate the patient.
U.S. Pat. No. 4,861,581 discloses a process comprising the steps of obtaining monoclonal antibodies that are specific to an internal cellular component of neoplastic and normal cells of the mammal but not to external components, labeling the monoclonal antibody, contacting the labeled antibody with tissue of a mammal that has received therapy to kill neoplastic cells, and determining the effectiveness of therapy by measuring the binding of the labeled antibody to the internal cellular component of the degenerating neoplastic cells. In preparing antibodies directed to human intracellular antigens, the patentee recognizes that malignant cells represent a convenient source of such antigens.
U.S. Pat. No. 5,171,665 provides a novel antibody and method for its production. Specifically, the patent teaches formation of a monoclonal antibody which has the property of binding strongly to a protein antigen associated with human tumors, e.g. those of the colon and lung, while binding to normal cells to a much lesser degree.
U.S. Pat. No. 5,484,596 provides a method of cancer therapy comprising surgically removing tumor tissue from a human cancer patient, treating the tumor tissue to obtain tumor cells, irradiating the tumor cells to be viable but non-tumorigenic, and using these cells to prepare a vaccine for the patient capable of inhibiting recurrence of the primary tumor while simultaneously inhibiting metastases. The patent teaches the development of monoclonal antibodies which are reactive with surface antigens of tumor cells. As set forth at col. 4, lines 45 et seq., the patentees utilize autochthonous tumor cells in the development of monoclonal antibodies expressing active specific immunotherapy in human neoplasia.
U.S. Pat. No. 5,693,763 teaches a glycoprotein antigen characteristic of human carcinomas and not dependent upon the epithelial tissue of origin.
U.S. Pat. No. 5,783,186 is drawn to Anti-Her2 antibodies which induce apoptosis in Her2 expressing cells, hybridoma cell lines producing the antibodies, methods of treating cancer using the antibodies and pharmaceutical compositions including said antibodies.
U.S. Pat. No. 5,849,876 describes new hybridoma cell lines for the production of monoclonal antibodies to mucin antigens purified from tumor and non-tumor tissue sources.
U.S. Pat. No. 5,869,268 is drawn to a method for generating a human lymphocyte producing an antibody specific to a desired antigen, a method for producing a monoclonal antibody, as well as monoclonal antibodies produced by the method. The patent is particularly drawn to the production of an anti-HD human monoclonal antibody useful for the diagnosis and treatment of cancers.
U.S. Pat. No. 5,869,045 relates to antibodies, antibody fragments, antibody conjugates and single-chain immunotoxins reactive with human carcinoma cells. The mechanism by which these antibodies function is two-fold, in that the molecules are reactive with cell membrane antigens present on the surface of human carcinomas, and further in that the antibodies have the ability to internalize within the carcinoma cells, subsequent to binding, making them especially useful for forming antibody-drug and antibody-toxin conjugates. In their unmodified form the antibodies also manifest cytotoxic properties at specific concentrations.
U.S. Pat. No. 5,780,033 discloses the use of autoantibodies for tumor therapy and prophylaxis. However, this antibody is an antinuclear autoantibody from an aged mammal. In this case, the autoantibody is said to be one type of natural antibody found in the immune system. Because the autoantibody comes from “an aged mammal”, there is no requirement that the autoantibody actually comes from the patient being treated. In addition the patent discloses natural and monoclonal antinuclear autoantibody from an aged mammal, and a hybridoma cell line producing a monoclonal antinuclear autoantibody.
U.S. Pat. No. 5,850,854 discloses a specific antibody, BR110 directed against GA733-1. This patent discloses in vitro function for BR110 as an immunotoxin conjugate. There was no in vitro function as a naked antibody disclosed for this antibody. There was also no in vivo function disclosed for this antibody.
U.S. Pat. No. 6,653,104 claims immunotoxin-conjugated antibodies, including but not limited to RS7, directed against a host of antigens, including but not limited to EGP-1. The immunotoxin is limited to those possessing ribonucleolytic activity. However, the examples disclose only a specific immunotoxin-conjugated antibody, LL2, directed against CD22. There was no in vitro or in vivo function for RS7 disclosed in this application.
U.S. Application No. 20040001825A1 discloses a specific antibody, RS7 directed against EGP-1. This application discloses in vitro function for RS7 as a radiolabeled conjugate. There was no in vitro function as a naked antibody disclosed for this antibody. This application also discloses in vivo function for RS7 resulting from radiolabled and unlabeled conjugate administered sequentially. However, this study was limited to one patient and it is unknown whether any of the observed function was due to the unlabeled antibody. There was no in vivo function for RS7 resulting from the administration of the naked antibody.